The present invention relates to fifth wheel coupling assemblies, and in particular to a slider assembly for adjustably supporting a fifth wheel hitch assembly from a frame of an associated vehicle.
Fifth wheel hitch assemblies are used in a wide variety of applications to releasably couple a trailer to an associated towing vehicle, including heavy-duty, over-the-road, tractors. The frames of the tractors, to which the fifth wheel assemblies are mounted, typically comprise a pair of longitudinally-extending C-shaped channel members that are supported by the wheel and axle members of the vehicle. The channel members are laterally spaced apart from one another such that they provide a planar surface for resisting normal and twisting forces after the fifth wheel is secured thereupon and placed in operation, thereby transferring the payload of the trailer equally onto each of the channel members. The fifth wheel hitch assembly can be mounted on the truck frame in a number of various ways, such as by utilizing drop-over angle brackets or flat mounting plates.
The drop-over method utilizes an L-shaped angle member which conforms and communicates with the top and vertical edges of each of the channels, having a long vertical leg securely fixed to an outboard vertical side of the associated channel, and a horizontal leg of the drop-over bracket that typically includes an arcuately-shaped mounting bracket which is welded thereon. The arcuate mounting bracket lies generally above the top horizontal leg of the C-shaped channel, and includes a horizontally-aligned bore for accepting a coupling cross pin which is in communication with the fifth wheel frame work. Specifically, the fifth wheel frame work includes a flange on one or each peripheral edge that communicates with the arcuate mounting bracket, thereby allowing the flange ports on each flange to be horizontally aligned with the mounting bracket bore for pinning the fifth wheel to the drop-over angle mounting bracket and hence, to the tractor frame. Although the drop-over brackets transmit lateral inertial forces which are caused by curving and rocking of the fifth wheel into the frame, drop-over arrangements are best suited for resisting longitudinal forces and moments caused from acceleration, deceleration, as well as the downward forces acting on the ramps eccentric to the rear of the bracket pivot center during coupling.
Alternatively, a flat plate mounting assembly includes a rectangular, planar plate of steel that is secured on top of each of the channel members, with the lateral sides of the plate extending slightly beyond each channel. In order to transfer loads from the plate to the frame, a section of L-shaped angle, typically referred to as the outboard angle, is used to support the plate directly below the overhang. The outboard angle member is also secured to the tractor channel and the flat mounting plate by securing a horizontal leg thereof to the bottom side of the mounting plate and securing a vertical leg thereof to the vertical wall of the associated channel. Similar arcuate mounting brackets to those discussed above are welded to the top of the mounting plate. The flat mounting plate method of attachment offers increased fatigue strength when compared to the drop-over mounting assembly because the lateral forces and moments that work upon the arcuate mounting bracket are first distributed throughout the entire flat plate surface area before they are distributed and transferred into the outboard angle member, thereby increasing the surface area over which the load is distributed. However, one significant disadvantage of the flat plat mounting arrangement is the use of a heavy steel plate adding to the weight and total cost of the overall assembly.
Another significant disadvantage to each of these arrangements as discussed above is the significant welding the overall assemblies require, thereby increasing the manufacturing costs and decreasing the adjustability and variability of the overall assembly once installed. Still further, these designs typically extend below the upper surface of the associated vehicle frame or channel members, thereby requiring precise placement of laterally-extending structural frame members of either the truck frame or the fifth wheel slider assembly, and/or rerouting of associated electrical and hydraulic lines.
Still further, typical fifth wheel assemblies that provide for slidable adjustment of the associated fifth wheel hitch plate with respect to the vehicle frame members require the use of separate stock members affixed to either a component of the fifth wheel assembly or the frame rails, in order to limit the travel of the fifth wheel hitch plate with respect to the vehicle frame rails, thereby adding to the costs associated with the manufacture of the fifth wheel hitch assembly.
A fifth wheel hitch assembly is desired that reduces the number of components necessary to provide a slidable adjustment of an associated hitch plate with respect to supporting vehicle frame rails, while simultaneously providing for easy adjustment and replacement of worn or damaged components. The fifth wheel hitch assembly should further reduce the associated weight, reduce manufacturing costs by eliminating welding and other time consuming processes, provide a modular design that allows easy assembly and/or retrofitting, and allows for use with various truck frame designs without requiring significant reworking to either the hitch assembly of the truck frame.